Chemical and cultural management strategies for glyphosate-resistant sourgrass in central Brazil

Correia, Núbia Maria

doi:10.1590/S1678-3921.pab2023.v58.02900

Núbia Maria Correia ^✉✉ Corresponding author

Embrapa Cerrados, BR 020, Km 18, Caixa Postal 08223, CEP 73310-970 Planaltina, DF, Brazil.

https://orcid.org/0000-0002-5045-9798

✉ Corresponding author

Figures (1)
Tables (5)

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Figure 1
Total monthly rainfall and mean minimum and maximum monthly air temperatures recorded during the experimental period from November 2020 to November 2021 at the climatological station of Embrapa Cerrados, located in the municipality of Planaltina, in Distrito Federal, Brazil.

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Table 1
Control of adult sourgrass (Digitaria insularis) plants at 15, 30, 45, and 60 days after the first herbicide application (DAFA) and at soybean (Glycine max) pre-harvest at 137 DAFA as affected by herbicide treatments at soybean pre-sowing and post-emergence⁽¹ (1) Means followed by equal letters, in the columns, do not differ from each other by Tukey’s test, at 5% probability. ⁾.

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Table 2
Control of seedlings of sourgrass (Digitaria insularis) and of other weed species at 30, 45, and 60 days after the first herbicide application (DAFA) and at soybean pre-harvest at 137 DAFA as affected by herbicide treatments at soybean (Glycine max) pre-sowing and post-emergence⁽¹ (1) Means followed by equal letters, in the columns, do not differ from each other by Tukey’s test, at 5% probability. ⁾.

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Table 3
Soybean (Glycine max) plant population and grain yield as affected by herbicide treatments applied at pre-sowing and post-emergence⁽¹ (1) Means followed by equal letters, in the columns, do not differ from each other by Tukey’s test, at 5% probability. ⁾.

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Table 4
Forage plant density at 30 days after soybean (Glycine max) harvest (DAH), soil cover by forage, and shoot dry matter production at 240 DAH as affected by the species established in the area after soybean harvest in the off-season⁽¹ (1) Means followed by equal letters, in the columns, do not differ from each other by Tukey’s test, at 5% probability. **Significant by the F-test, at 1% probability. ⁾.

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Table 5
Infestation by sourgrass (Digitaria insularis) and other weed species, as well as sourgrass density (plants per square meter), at 240 days after soybean (Glycine max) harvest as affected by herbicide treatments for the control of sourgrass in the soybean crop, combined with the maintenance or not (fallow) of forage species in the off-season⁽¹ (1) Means followed by equal letters, in the columns, do not differ from each other by Tukey’s test, at 5% probability. ⁾.

Id.	Treatment/Control		Control of adult sourgrass (%)
Id.	Pre-sowing	Post-emergence	15	30	45	60	137
1	Clethodim/Glyphosate	Clethodim/Glyphosate	76.25b	85.62a	97.50a	93.75a	95.00a
2	Haloxyfop/Glyphosate	Haloxyfop/Glyphosate	75.62b	86.88a	98.12a	95.62a	96.25a
3	Clethodim/Glyphosate	Haloxyfop/Glyphosate	74.38b	85.00a	96.88a	93.12a	96.25a
4	Clethodim/Glyphosate and Glufosinate/S-metolachlor⁽² (2) First application of clethodim + glyphosate and a sequential application of glufosinate ammonium + s-metolachlor after 8 days. **Significant by the F-test, at 1% probability. ⁾	Glyphosate	91.25a	86.88a	91.88b	93.75a	92.50a
5	Glyphosate	Glyphosate	15.00c	30.00b	42.50c	35.00b	26.25b
	Least significant difference (LSD)		5.21	3.13	4.52	7.44	6.43
	F_Treatments		653.39^**	1,307.59^**	579.08^**	256.69^**	466.54^**
	Coefficient of variation (CV, %)		3.48	1.85	2.35	4.01	3.51

Id.	Treatment/Control		Control of seedlings of sourgrass (%)⁽² (2) Control was defined as the percentage of seedlings of the Cenchrus echinatus, Chamaesyce hirta, Commelina benghalensis, Conyza sumatrensis, Eleusine indica, Portulaca oleracea weed species and of sourgrass present in the experimental unit. ⁾
Id.	Pre-sowing	Post-emergence	30	45	60	137
1	Clethodim/Glyphosate	Clethodim/Glyphosate	0.00c	85.00cd	79.38c	90.62c
2	Haloxyfop/Glyphosate	Haloxyfop/Glyphosate	0.00c	87.5bc	80.00c	92.50bc
3	Clethodim/Glyphosate	Haloxyfop/Glyphosate	0.00c	81.25d	79.38c	94.38abc
4	Clethodim/Glyphosate and Glufosinate/S-metolachlor⁽³ (3) First application of clethodim + glyphosate and a sequential application of glufosinate ammonium + s-metolachlor after 8 days. **Significant by the F-test, at 1% probability. ⁾	Glyphosate	76.25b	91.25b	85.62b	95.62ab
5	Glyphosate	Glyphosate	100.00a	100.00a	100.00a	98.75a
	Least significant difference (LSD)		4.83	4.37	3.13	4.57
	F_Treatments		2,094.82^**	54.50^**	162.73^**	9.30^**
	Coefficient of variation (CV, %)		6.07	2.18	1.64	2.15

Id.	Treatment/Control		Population (1,000 plants per ha)	Grain production
Id.	Pre-sowing	Post-emergence	Population (1,000 plants per ha)	(kg ha^-1)	(g per plant)
1	Clethodim/Glyphosate	Clethodim/Glyphosate	218.75a	3,032.46a	13.96a
2	Haloxyfop/Glyphosate	Haloxyfop/Glyphosate	224.17a	3,165.38a	14.14a
3	Clethodim/Glyphosate	Haloxyfop/Glyphosate	229.17a	3,200.49a	13.97a
4	Clethodim/Glyphosate and Glufosinate/S-metolachlor⁽² (2) First application of clethodim + glyphosate and a sequential application of glufosinate ammonium + s-metolachlor after 8 days. **Significant by the F-test, at 1% probability. ⁾	Glyphosate	229.58a	3,362.43a	13.65a
5	Glyphosate	Glyphosate	146.67b	2,170.82b	14.67a
6	Control - infested		14.17c	39.95c	3.23b
7	Control - weeding		218.33a	3,305.76a	15.12a
	Least significant difference (LSD)		25.39	660.41	3.68
	F_Treatments		216.65^**	72.52^**	29.13^**
	Coefficient of variation (CV, %)		5.94	10.82	12.29

Forage	Density (plants per m^-2)	Soil cover (%)	Dry matter (kg ha^-1)
With no forage (fallow)	-	-	-
'Massai' (Panicum maximum)	7.78a	58.12b	3,872.96ab
'BRS Tamani' (P. maximum)	3.12bc	76.88a	4,968.59a
'BRS Zuri' (P. maximum)	4.03b	72.50a	4,780.53a
Urochloa ruziziensis	1.18c	51.25b	2,767.96b
Least significant difference (LSD)	2.69	11.16	1,265.36
Herbicide	0.14	5.25	0.64
Forage	15.13^**	16.50^**	9.02^**
Herbicide x Forage	0.38	0.61	1.48
Coefficient of variation (CV, %)	40.70	18.29	32.73

Treatment during the crop cycle⁽³ (3) The control treatments (isolated application of glyphosate, infested control, and weeding control) were compared with each other and with the treatments of interest (factorial) through orthogonal contrasts.. **Significant by the F-test, at 1% probability. ⁾	Treatment in the off-season	Infestation (%)⁽² (2) Infestation was defined according to the weed species present in the experimental unit, which were: Bidens subalternans, Chamaesyce hirta, Cenchrus echinatus, Commelina benghalensis, Conyza sumatrensis, Eleusine indica, Emilia sonchifolia, Euphorbia heterophylla, Galinsoga parviflora, Nicandra physalodes, Portulaca oleracea, Richardia brasiliensis, Rhynchelytrum repens, Sida rhombifolia, Solanum americanum, and Tridax procumbens. ⁾		Sourgrass density (plants per m²)
	Treatment in the off-season	Sourgrass	Other species	Sourgrass density (plants per m²)
Herbicide	With no forage (fallow)	49.06b	47.50d	10.50b
	'Massai' (Panicum maximum)	17.50a	24.38bc	3.75a
	'BRS Tamani' (P. maximum)	8.75a	13.75a	2.00a
	'BRS Zuri' (P. maximum)	6.25a	20.00ab	1.50a
	Urochloa ruziziensis	16.88a	30.94c	3.75a
Least significant difference (LSD)		12.35	9.89	2.64
Glyphosate	Fallow	93.75	5.00	24.50
Control infested	Fallow	93.75	6.25	25.25
Control weeding	Fallow	88.75	11.25	20.00
Herbicide		3.33	0.98	5.33
Forage		30.59^**	27.06^**	36.58^**
Herbicide x forage		1.30	2.54	1.30
Coefficient of variation (CV, %)		42.98	36.35	52.97

[TFN01] ⁽¹⁾
Means followed by equal letters, in the columns, do not differ from each other by Tukey’s test, at 5% probability.

[TFN02] ⁽²⁾
First application of clethodim + glyphosate and a sequential application of glufosinate ammonium + s-metolachlor after 8 days. **Significant by the F-test, at 1% probability.

Chemical and cultural management strategies for glyphosate-resistant sourgrass in central Brazil

Estratégias de manejo químico e cultural de capim-amargoso resistente ao glifosato no Brasil Central

Abstract